]> wimlib.net Git - wimlib/blobdiff - src/resource.c
read_compressed_resource(): Fix format strings
[wimlib] / src / resource.c
index 600bf5ba1321bb772f4d788ccfe33aad456c661b..8d61761414c9b718a1e4b0dab9312359616711ab 100644 (file)
@@ -1,44 +1,56 @@
 /*
  * resource.c
  *
- * Read uncompressed and compressed metadata and file resources.
- *
- * Copyright (C) 2010 Carl Thijssen
- * Copyright (C) 2012 Eric Biggers
+ * Read uncompressed and compressed metadata and file resources from a WIM file.
+ */
+
+/*
+ * Copyright (C) 2012, 2013 Eric Biggers
  *
- * wimlib - Library for working with WIM files
+ * This file is part of wimlib, a library for working with WIM files.
  *
- * This library is free software; you can redistribute it and/or modify it under
- * the terms of the GNU Lesser General Public License as published by the Free
- * Software Foundation; either version 2.1 of the License, or (at your option) any
- * later version.
+ * wimlib is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
  *
- * This library is distributed in the hope that it will be useful, but WITHOUT ANY
- * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
- * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
+ * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU Lesser General Public License along
- * with this library; if not, write to the Free Software Foundation, Inc., 59
- * Temple Place, Suite 330, Boston, MA 02111-1307 USA 
+ * You should have received a copy of the GNU General Public License along with
+ * wimlib; if not, see http://www.gnu.org/licenses/.
  */
 
 #include "wimlib_internal.h"
-#include "io.h"
+#include "dentry.h"
+#include "lookup_table.h"
+#include "buffer_io.h"
 #include "lzx.h"
 #include "xpress.h"
-#include "dentry.h"
-#include <unistd.h>
+#include "sha1.h"
+
 #include <errno.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#ifdef WITH_NTFS_3G
+#include <time.h>
+#include <ntfs-3g/attrib.h>
+#include <ntfs-3g/inode.h>
+#include <ntfs-3g/dir.h>
+#endif
 
-/* 
+/*
  * Reads all or part of a compressed resource into an in-memory buffer.
  *
  * @fp:                The FILE* for the WIM file.
- * @resource_compressed_size:           The compressed size of the resource.  
+ * @resource_compressed_size:           The compressed size of the resource.
  * @resource_uncompressed_size:  The uncompressed size of the resource.
  * @resource_offset:            The offset of the start of the resource from
  *                                     the start of the stream @fp.
- * @resource_ctype:    The compression type of the resource. 
+ * @resource_ctype:    The compression type of the resource.
  * @len:               The number of bytes of uncompressed data to read from
  *                             the resource.
  * @offset:            The offset of the bytes to read within the uncompressed
  *
  * Returns zero on success, nonzero on failure.
  */
-static int read_compressed_resource(FILE *fp, u64 resource_compressed_size, 
-                                   u64 resource_uncompressed_size, 
-                                   u64 resource_offset, int resource_ctype, 
+static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
+                                   u64 resource_uncompressed_size,
+                                   u64 resource_offset, int resource_ctype,
                                    u64 len, u64 offset, u8  contents_ret[])
 {
 
-       DEBUG2("comp size = %"PRIu64", "
-                       "uncomp size = %"PRIu64", "
-                       "res offset = %"PRIu64"\n",
-                       resource_compressed_size,
-                       resource_uncompressed_size,
-                       resource_offset);
-       DEBUG2("resource_ctype = %s, len = %"PRIu64", offset = %"PRIu64"\n",
-                               wimlib_get_compression_type_string(resource_ctype), 
-                                                               len, offset);
+       DEBUG2("comp size = %"PRIu64", uncomp size = %"PRIu64", "
+              "res offset = %"PRIu64"",
+              resource_compressed_size,
+              resource_uncompressed_size,
+              resource_offset);
+       DEBUG2("resource_ctype = %s, len = %"PRIu64", offset = %"PRIu64"",
+              wimlib_get_compression_type_string(resource_ctype), len, offset);
        /* Trivial case */
        if (len == 0)
                return 0;
 
-       int (*decompress)(const void *, uint, void *, uint);
+       int (*decompress)(const void *, unsigned, void *, unsigned);
        /* Set the appropriate decompress function. */
-       if (resource_ctype == WIM_COMPRESSION_TYPE_LZX)
+       if (resource_ctype == WIMLIB_COMPRESSION_TYPE_LZX)
                decompress = lzx_decompress;
        else
                decompress = xpress_decompress;
@@ -83,7 +93,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
         * The chunk offsets are measured relative to the end of the chunk
         * table.  The first chunk is omitted from the table in the WIM file
         * because its offset is implicitly given by the fact that it directly
-        * follows the chunk table and therefore must have an offset of 0. 
+        * follows the chunk table and therefore must have an offset of 0.
         */
 
        /* Calculate how many chunks the resource conists of in its entirety. */
@@ -131,7 +141,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        /* According to M$'s documentation, if the uncompressed size of
         * the file is greater than 4 GB, the chunk entries are 8-byte
         * integers.  Otherwise, they are 4-byte integers. */
-       u64 chunk_entry_size = (resource_uncompressed_size >= (u64)1 << 32) ? 
+       u64 chunk_entry_size = (resource_uncompressed_size >= (u64)1 << 32) ?
                                                                        8 : 4;
 
        /* Size of the full chunk table in the WIM file. */
@@ -145,17 +155,16 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
        /* Number of entries we need to actually read from the chunk
         * table (excludes the implicit first chunk). */
-       u64 num_needed_chunk_entries = (start_chunk == 0) ? 
+       u64 num_needed_chunk_entries = (start_chunk == 0) ?
                                num_needed_chunks - 1 : num_needed_chunks;
 
        /* Skip over unneeded chunk table entries. */
-       u64 file_offset_of_needed_chunk_entries = resource_offset + 
+       u64 file_offset_of_needed_chunk_entries = resource_offset +
                                start_table_idx * chunk_entry_size;
        if (fseeko(fp, file_offset_of_needed_chunk_entries, SEEK_SET) != 0) {
-               ERROR("Failed to seek to byte %"PRIu64" "
-                               "to read chunk table of compressed "
-                               "resource: %m\n", 
-                               file_offset_of_needed_chunk_entries);
+               ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" to read "
+                                "chunk table of compressed resource",
+                                file_offset_of_needed_chunk_entries);
                return WIMLIB_ERR_READ;
        }
 
@@ -177,23 +186,22 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        if (chunk_entry_size == 4) {
                u32 *entries = (u32*)chunk_tab_buf;
                while (num_needed_chunk_entries--)
-                       *chunk_tab_p++ = to_le32(*entries++);
+                       *chunk_tab_p++ = le32_to_cpu(*entries++);
        } else {
                u64 *entries = (u64*)chunk_tab_buf;
                while (num_needed_chunk_entries--)
-                       *chunk_tab_p++ = to_le64(*entries++);
+                       *chunk_tab_p++ = le64_to_cpu(*entries++);
        }
 
        /* Done with the chunk table now.  We must now seek to the first chunk
         * that is needed for the read. */
 
-       u64 file_offset_of_first_needed_chunk = resource_offset + 
+       u64 file_offset_of_first_needed_chunk = resource_offset +
                                chunk_table_size + chunk_offsets[0];
        if (fseeko(fp, file_offset_of_first_needed_chunk, SEEK_SET) != 0) {
-               ERROR("Failed to seek to byte %"PRIu64" "
-                               "to read first chunk of compressed "
-                               "resource: %m\n", 
-                               file_offset_of_first_needed_chunk);
+               ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" to read "
+                                "first chunk of compressed resource",
+                                file_offset_of_first_needed_chunk);
                return WIMLIB_ERR_READ;
        }
 
@@ -213,18 +221,19 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        /* Decompress all the chunks. */
        for (u64 i = start_chunk; i <= end_chunk; i++) {
 
-               DEBUG2("Chunk %"PRIu64" (start %"PRIu64", end %"PRIu64")\n",
-                               i, start_chunk, end_chunk);
+               DEBUG2("Chunk %"PRIu64" (start %"PRIu64", end %"PRIu64").",
+                      i, start_chunk, end_chunk);
 
                /* Calculate the sizes of the compressed chunk and of the
                 * uncompressed chunk. */
-               uint compressed_chunk_size, uncompressed_chunk_size;
+               unsigned compressed_chunk_size;
+               unsigned uncompressed_chunk_size;
                if (i != num_chunks - 1) {
                        /* All the chunks except the last one in the resource
                         * expand to WIM_CHUNK_SIZE uncompressed, and the amount
                         * of compressed data for the chunk is given by the
                         * difference of offsets in the chunk offset table. */
-                       compressed_chunk_size = chunk_offsets[i + 1 - start_chunk] - 
+                       compressed_chunk_size = chunk_offsets[i + 1 - start_chunk] -
                                                chunk_offsets[i - start_chunk];
                        uncompressed_chunk_size = WIM_CHUNK_SIZE;
                } else {
@@ -232,15 +241,15 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                         * bytes in the file resource, and the last uncompressed
                         * chunk has size equal to however many bytes are left-
                         * that is, the remainder of the uncompressed size when
-                        * divided by WIM_CHUNK_SIZE. 
+                        * divided by WIM_CHUNK_SIZE.
                         *
                         * Note that the resource_compressed_size includes the
                         * chunk table, so the size of it must be subtracted. */
-                       compressed_chunk_size = resource_compressed_size - 
+                       compressed_chunk_size = resource_compressed_size -
                                                chunk_table_size -
                                                chunk_offsets[i - start_chunk];
 
-                       uncompressed_chunk_size = resource_uncompressed_size % 
+                       uncompressed_chunk_size = resource_uncompressed_size %
                                                                WIM_CHUNK_SIZE;
 
                        /* If the remainder is 0, the last chunk actually
@@ -249,8 +258,9 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                                uncompressed_chunk_size = WIM_CHUNK_SIZE;
                }
 
-               DEBUG2("compressed_chunk_size = %u, uncompressed_chunk_size = %u\n",
-                               compressed_chunk_size, uncompressed_chunk_size);
+               DEBUG2("compressed_chunk_size = %u, "
+                      "uncompressed_chunk_size = %u",
+                      compressed_chunk_size, uncompressed_chunk_size);
 
 
                /* Figure out how much of this chunk we actually need to read */
@@ -266,12 +276,12 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                        end_offset = WIM_CHUNK_SIZE - 1;
 
                u64 partial_chunk_size = end_offset + 1 - start_offset;
-               bool is_partial_chunk = (partial_chunk_size != 
+               bool is_partial_chunk = (partial_chunk_size !=
                                                uncompressed_chunk_size);
 
-               DEBUG2("start_offset = %u, end_offset = %u\n", start_offset,
-                                       end_offset);
-               DEBUG2("partial_chunk_size = %u\n", partial_chunk_size);
+               DEBUG2("start_offset = %"PRIu64", end_offset = %"PRIu64"",
+                      start_offset, end_offset);
+               DEBUG2("partial_chunk_size = %"PRIu64"", partial_chunk_size);
 
                /* This is undocumented, but chunks can be uncompressed.  This
                 * appears to always be the case when the compressed chunk size
@@ -281,12 +291,12 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
                        if (start_offset != 0) {
                                if (fseeko(fp, start_offset, SEEK_CUR) != 0) {
-                                       ERROR("Uncompressed partial chunk "
-                                                       "fseek() error: %m\n");
+                                       ERROR_WITH_ERRNO("Uncompressed partial "
+                                                        "chunk fseek() error");
                                        return WIMLIB_ERR_READ;
                                }
                        }
-                       if (fread(out_p, 1, partial_chunk_size, fp) != 
+                       if (fread(out_p, 1, partial_chunk_size, fp) !=
                                        partial_chunk_size)
                                goto err;
                } else {
@@ -294,7 +304,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                        int ret;
 
                        /* Read the compressed data into compressed_buf. */
-                       if (fread(compressed_buf, 1, compressed_chunk_size, 
+                       if (fread(compressed_buf, 1, compressed_chunk_size,
                                                fp) != compressed_chunk_size)
                                goto err;
 
@@ -305,14 +315,13 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
                                ret = decompress(compressed_buf,
                                                compressed_chunk_size,
-                                               uncompressed_buf, 
+                                               uncompressed_buf,
                                                uncompressed_chunk_size);
                                if (ret != 0)
                                        return WIMLIB_ERR_DECOMPRESSION;
                                memcpy(out_p, uncompressed_buf + start_offset,
                                                partial_chunk_size);
                        } else {
-                               DEBUG2("out_p = %p\n");
                                ret = decompress(compressed_buf,
                                                compressed_chunk_size,
                                                out_p,
@@ -331,137 +340,37 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
 err:
        if (feof(fp))
-               ERROR("Unexpected EOF in compressed file resource\n");
+               ERROR("Unexpected EOF in compressed file resource");
        else
-               ERROR("Error reading compressed file resource: %m\n");
+               ERROR_WITH_ERRNO("Error reading compressed file resource");
        return WIMLIB_ERR_READ;
 }
 
-/* 
+/*
  * Reads uncompressed data from an open file stream.
  */
-int read_uncompressed_resource(FILE *fp, u64 offset, u64 len, 
-                                       u8 contents_ret[])
+int read_uncompressed_resource(FILE *fp, u64 offset, u64 len,
+                              u8 contents_ret[])
 {
        if (fseeko(fp, offset, SEEK_SET) != 0) {
                ERROR("Failed to seek to byte %"PRIu64" of input file "
-                               "to read uncompressed resource "
-                               "(len = %"PRIu64")!\n", offset, len);
+                     "to read uncompressed resource (len = %"PRIu64")",
+                     offset, len);
                return WIMLIB_ERR_READ;
        }
        if (fread(contents_ret, 1, len, fp) != len) {
                if (feof(fp)) {
-                       ERROR("Unexpected EOF in uncompressed file resource!\n");
+                       ERROR("Unexpected EOF in uncompressed file resource");
                } else {
                        ERROR("Failed to read %"PRIu64" bytes from "
-                                       "uncompressed resource at offset "
-                                       "%"PRIu64"\n", len, offset);
+                             "uncompressed resource at offset %"PRIu64,
+                             len, offset);
                }
                return WIMLIB_ERR_READ;
        }
        return 0;
 }
 
-/* 
- * Reads a WIM resource.
- *
- * @fp:                The FILE* for the WIM file.
- * @resource_size:             The compressed size of the resource.
- * @resource_original_size:    The uncompressed size of the resource.
- * @resource_offset:           The offset of the resource in the stream @fp.
- * @resource_ctype:            The compression type of the resource.
- *                             (WIM_COMPRESSION_TYPE_*)
- * @len:               How many bytes of the resource should be read.
- * @offset:            The offset within the resource at which the read
- *                             will occur.
- *
- *                     To read the whole file resource, specify offset =
- *                     0 and len = resource_original_size, or call
- *                     read_full_resource().
- *
- * @contents_ret:      An array, that must have length at least @len,
- *                             into which the uncompressed contents of
- *                             the file resource starting at @offset and 
- *                             continuing for @len bytes will be written.
- *
- * @return:            Zero on success, nonzero on failure. Failure may be due to
- *                     being unable to read the data from the WIM file at the
- *                     specified length and offset, or it may be due to the
- *                     compressed data (if the data is compressed) being
- *                     invalid.
- */
-int read_resource(FILE *fp, u64 resource_size, u64 resource_original_size,
-                 u64 resource_offset, int resource_ctype, u64 len, 
-                 u64 offset, void *contents_ret)
-{
-       if (resource_ctype == WIM_COMPRESSION_TYPE_NONE) {
-               if (resource_size != resource_original_size) {
-                       ERROR("Resource with original size %"PRIu64" "
-                                       "bytes is marked as uncompressed, \n",
-                                       resource_original_size);
-                       ERROR("    but its actual size is %"PRIu64" "
-                                                               "bytes!\n",
-                                       resource_size);
-                       return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
-               }
-               return read_uncompressed_resource(fp, 
-                               resource_offset + offset, 
-                               len, contents_ret);
-       } else {
-               return read_compressed_resource(fp, resource_size,
-                               resource_original_size, resource_offset,
-                               resource_ctype, len, offset, contents_ret);
-       }
-}
-
-
-/* 
- * Extracts the first @size bytes file resource specified by @entry to the open
- * file @fd.  Returns nonzero on error.
- *
- * XXX
- * This function is somewhat redundant with uncompress_resource(). The
- * main difference is that this function writes to a file descriptor using
- * low-level calls to write() rather than to a FILE* with fwrite(); also this
- * function allows only up to @size bytes to be extracted.
- */
-int extract_resource_to_fd(WIMStruct *w, const struct resource_entry *entry, 
-                          int fd, u64 size)
-{
-       u64 num_chunks;
-       u64 n;
-       u8 buf[min(size, WIM_CHUNK_SIZE)];
-       int res_ctype;
-       u64 offset;
-       u64 i;
-       int ret;
-
-       errno = 0;
-
-       num_chunks = (size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
-       n = WIM_CHUNK_SIZE;
-       res_ctype = wim_resource_compression_type(w, entry);
-       offset = 0;
-       for (i = 0; i < num_chunks; i++) {
-               if (i == num_chunks - 1) {
-                       n = size % WIM_CHUNK_SIZE;
-                       if (n == 0) {
-                               n = WIM_CHUNK_SIZE;
-                       }
-               }
-
-               ret = read_resource(w->fp, entry->size, entry->original_size,
-                                   entry->offset, res_ctype, n, offset, buf);
-               if (ret != 0)
-                       return ret;
-
-               if (full_write(fd, buf, n) != n)
-                       return WIMLIB_ERR_WRITE;
-               offset += n;
-       }
-       return ret;
-}
-
 /* Reads the contents of a struct resource_entry, as represented in the on-disk
  * format, from the memory pointed to by @p, and fills in the fields of @entry.
  * A pointer to the byte after the memory read at @p is returned. */
@@ -474,8 +383,21 @@ const u8 *get_resource_entry(const u8 *p, struct resource_entry *entry)
        p = get_u8(p, &flags);
        entry->size = size;
        entry->flags = flags;
+
+       /* offset and original_size are truncated to 62 bits to avoid possible
+        * overflows, when converting to a signed 64-bit integer (off_t) or when
+        * adding size or original_size.  This is okay since no one would ever
+        * actually have a WIM bigger than 4611686018427387903 bytes... */
        p = get_u64(p, &entry->offset);
+       if (entry->offset & 0xc000000000000000ULL) {
+               WARNING("Truncating offset in resource entry");
+               entry->offset &= 0x3fffffffffffffffULL;
+       }
        p = get_u64(p, &entry->original_size);
+       if (entry->original_size & 0xc000000000000000ULL) {
+               WARNING("Truncating original_size in resource entry");
+               entry->original_size &= 0x3fffffffffffffffULL;
+       }
        return p;
 }
 
@@ -491,127 +413,313 @@ u8 *put_resource_entry(u8 *p, const struct resource_entry *entry)
        return p;
 }
 
-/* Given the compression type for the WIM file as a whole as the flags field of
- * a resource entry, returns the compression type for that resource entry. */
-int resource_compression_type(int wim_ctype, int reshdr_flags)
+#ifdef WITH_FUSE
+static FILE *wim_get_fp(WIMStruct *w)
 {
-       if (wim_ctype == WIM_COMPRESSION_TYPE_NONE) {
-               return WIM_COMPRESSION_TYPE_NONE;
-       } else {
-               if (reshdr_flags & WIM_RESHDR_FLAG_COMPRESSED)
-                       return wim_ctype;
-               else
-                       return WIM_COMPRESSION_TYPE_NONE;
+       pthread_mutex_lock(&w->fp_tab_mutex);
+       FILE *fp;
+
+       wimlib_assert(w->filename != NULL);
+
+       for (size_t i = 0; i < w->num_allocated_fps; i++) {
+               if (w->fp_tab[i]) {
+                       fp = w->fp_tab[i];
+                       w->fp_tab[i] = NULL;
+                       goto out;
+               }
        }
+       DEBUG("Opening extra file descriptor to `%s'", w->filename);
+       fp = fopen(w->filename, "rb");
+       if (!fp)
+               ERROR_WITH_ERRNO("Failed to open `%s'", w->filename);
+out:
+       pthread_mutex_unlock(&w->fp_tab_mutex);
+       return fp;
 }
 
-/* 
- * Reads the metadata metadata resource from the WIM file.  The metadata
- * resource consists of the security data, followed by the directory entry for
- * the root directory, followed by all the other directory entries in the
- * filesystem.  The subdir_offset field of each directory entry gives the start
- * of its child entries from the beginning of the metadata resource.  An
- * end-of-directory is signaled by a directory entry of length '0', really of
- * length 8, because that's how long the 'length' field is.
+static int wim_release_fp(WIMStruct *w, FILE *fp)
+{
+       int ret = 0;
+       FILE **fp_tab;
+
+       pthread_mutex_lock(&w->fp_tab_mutex);
+
+       for (size_t i = 0; i < w->num_allocated_fps; i++) {
+               if (w->fp_tab[i] == NULL) {
+                       w->fp_tab[i] = fp;
+                       goto out;
+               }
+       }
+
+       fp_tab = REALLOC(w->fp_tab, sizeof(FILE*) * (w->num_allocated_fps + 4));
+       if (!fp_tab) {
+               ret = WIMLIB_ERR_NOMEM;
+               goto out;
+       }
+       w->fp_tab = fp_tab;
+       memset(&w->fp_tab[w->num_allocated_fps], 0, 4 * sizeof(FILE*));
+       w->fp_tab[w->num_allocated_fps] = fp;
+       w->num_allocated_fps += 4;
+out:
+       pthread_mutex_unlock(&w->fp_tab_mutex);
+       return ret;
+}
+#endif
+
+/*
+ * Reads some data from the resource corresponding to a WIM lookup table entry.
  *
- * @fp:                The FILE* for the input WIM file.
- * @res_entry: The resource entry for the metadata resource (a.k.a the metadata
- *                     for the metadata)
- * @wim_ctype: The compression type of the WIM file.
- * @root_dentry_p:     A pointer to a pointer to a struct dentry structure into which the 
- *             root dentry is allocated and returned.
+ * @lte:       The WIM lookup table entry for the resource.
+ * @buf:       Buffer into which to write the data.
+ * @size:      Number of bytes to read.
+ * @offset:    Offset at which to start reading the resource.
  *
- * @return:    True on success, false on failure.
+ * Returns zero on success, nonzero on failure.
  */
-int read_metadata_resource(FILE *fp, const struct resource_entry *res_entry,
-                          int wim_ctype, struct dentry **root_dentry_p)
+int read_wim_resource(const struct wim_lookup_table_entry *lte, u8 buf[],
+                     size_t size, u64 offset, int flags)
 {
-       u8 *buf;
        int ctype;
-       u32 dentry_offset;
-       int ret;
-       struct dentry *dentry;
+       int ret = 0;
+       FILE *fp;
 
-       DEBUG("Reading metadata resource: length = %lu, offset = %lu\n",
-                       res_entry->original_size, res_entry->offset);
+       /* We shouldn't be allowing read over-runs in any part of the library.
+        * */
+       if (flags & WIMLIB_RESOURCE_FLAG_RAW)
+               wimlib_assert(offset + size <= lte->resource_entry.size);
+       else
+               wimlib_assert(offset + size <= lte->resource_entry.original_size);
+
+       switch (lte->resource_location) {
+       case RESOURCE_IN_WIM:
+               /* The resource is in a WIM file, and its WIMStruct is given by
+                * the lte->wim member.  The resource may be either compressed
+                * or uncompressed. */
+               wimlib_assert(lte->wim != NULL);
+
+               #ifdef WITH_FUSE
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       fp = wim_get_fp(lte->wim);
+                       if (!fp)
+                               return WIMLIB_ERR_OPEN;
+               } else
+               #endif
+               {
+                       wimlib_assert(!(flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED));
+                       wimlib_assert(lte->wim->fp != NULL);
+                       fp = lte->wim->fp;
+               }
 
-       if (res_entry->original_size < 8) {
-               ERROR("Expected at least 8 bytes for the metadata "
-                               "resource!\n");
-               return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
-       }
+               ctype = wim_resource_compression_type(lte);
 
-       /* Allocate memory for the uncompressed metadata resource. */
-       buf = MALLOC(res_entry->original_size);
+               wimlib_assert(ctype != WIMLIB_COMPRESSION_TYPE_NONE ||
+                             (lte->resource_entry.original_size ==
+                              lte->resource_entry.size));
 
-       if (!buf) {
-               ERROR("Failed to allocate %"PRIu64" bytes for uncompressed "
-                               "metadata resource!\n",
-                               res_entry->original_size);
-               return WIMLIB_ERR_NOMEM;
+               if ((flags & WIMLIB_RESOURCE_FLAG_RAW)
+                   || ctype == WIMLIB_COMPRESSION_TYPE_NONE)
+                       ret = read_uncompressed_resource(fp,
+                                                        lte->resource_entry.offset + offset,
+                                                        size, buf);
+               else
+                       ret = read_compressed_resource(fp,
+                                                      lte->resource_entry.size,
+                                                      lte->resource_entry.original_size,
+                                                      lte->resource_entry.offset,
+                                                      ctype, size, offset, buf);
+       #ifdef WITH_FUSE
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       int ret2 = wim_release_fp(lte->wim, fp);
+                       if (ret == 0)
+                               ret = ret2;
+               }
+       #endif
+               break;
+       case RESOURCE_IN_STAGING_FILE:
+       case RESOURCE_IN_FILE_ON_DISK:
+               /* The resource is in some file on the external filesystem and
+                * needs to be read uncompressed */
+               wimlib_assert(lte->file_on_disk != NULL);
+               BUILD_BUG_ON(&lte->file_on_disk != &lte->staging_file_name);
+               /* Use existing file pointer if available; otherwise open one
+                * temporarily */
+               if (lte->file_on_disk_fp) {
+                       fp = lte->file_on_disk_fp;
+               } else {
+                       fp = fopen(lte->file_on_disk, "rb");
+                       if (!fp) {
+                               ERROR_WITH_ERRNO("Failed to open the file "
+                                                "`%s'", lte->file_on_disk);
+                               ret = WIMLIB_ERR_OPEN;
+                               break;
+                       }
+               }
+               ret = read_uncompressed_resource(fp, offset, size, buf);
+               if (fp != lte->file_on_disk_fp)
+                       fclose(fp);
+               break;
+#if defined(__CYGWIN__) || defined(__WIN32__)
+       case RESOURCE_WIN32:
+               wimlib_assert(lte->file_on_disk_fp != NULL);
+               ret = win32_read_file(lte->file_on_disk, lte->file_on_disk_fp,
+                                     offset, size, buf);
+               break;
+#endif
+       case RESOURCE_IN_ATTACHED_BUFFER:
+               /* The resource is directly attached uncompressed in an
+                * in-memory buffer. */
+               wimlib_assert(lte->attached_buffer != NULL);
+               memcpy(buf, lte->attached_buffer + offset, size);
+               break;
+#ifdef WITH_NTFS_3G
+       case RESOURCE_IN_NTFS_VOLUME:
+               wimlib_assert(lte->ntfs_loc != NULL);
+               wimlib_assert(lte->attr != NULL);
+               if (lte->ntfs_loc->is_reparse_point)
+                       offset += 8;
+               if (ntfs_attr_pread(lte->attr, offset, size, buf) != size) {
+                       ERROR_WITH_ERRNO("Error reading NTFS attribute "
+                                        "at `%s'",
+                                        lte->ntfs_loc->path_utf8);
+                       ret = WIMLIB_ERR_NTFS_3G;
+               }
+               break;
+#endif
+       default:
+               wimlib_assert(0);
+               ret = -1;
+               break;
        }
+       return ret;
+}
 
-       /* Determine the compression type of the metadata resource. */
-       ctype = resource_compression_type(wim_ctype, res_entry->flags);
-
-       /* Read the metadata resource into memory.  (It may be compressed.) */
-       ret = read_full_resource(fp, res_entry->size, 
-                                res_entry->original_size, res_entry->offset, 
-                                ctype, buf);
-       if (ret != 0)
-               goto err1;
-
-       DEBUG("Finished reading metadata resource into memory.\n");
+/*
+ * Reads all the data from the resource corresponding to a WIM lookup table
+ * entry.
+ *
+ * @lte:       The WIM lookup table entry for the resource.
+ * @buf:       Buffer into which to write the data.  It must be at least
+ *             wim_resource_size(lte) bytes long.
+ *
+ * Returns 0 on success; nonzero on failure.
+ */
+int read_full_wim_resource(const struct wim_lookup_table_entry *lte, u8 buf[],
+                          int flags)
+{
+       return read_wim_resource(lte, buf, wim_resource_size(lte), 0, flags);
+}
 
-#if 0
-       /* Read the security data into a WIMSecurityData structure. */
-       if (!read_security_data(buf, res_entry->original_size, sd))
-               goto err1;
-#endif
+/* Extracts the first @size bytes of a WIM resource to somewhere.  In the
+ * process, the SHA1 message digest of the resource is checked if the full
+ * resource is being extracted.
+ *
+ * @extract_chunk is a function that is called to extract each chunk of the
+ * resource. */
+int extract_wim_resource(const struct wim_lookup_table_entry *lte,
+                        u64 size,
+                        extract_chunk_func_t extract_chunk,
+                        void *extract_chunk_arg)
+{
+       u64 bytes_remaining = size;
+       u8 buf[min(WIM_CHUNK_SIZE, bytes_remaining)];
+       u64 offset = 0;
+       int ret = 0;
+       u8 hash[SHA1_HASH_SIZE];
+       bool check_hash = (size == wim_resource_size(lte));
+       SHA_CTX ctx;
+
+       if (check_hash)
+               sha1_init(&ctx);
+
+       while (bytes_remaining) {
+               u64 to_read = min(bytes_remaining, sizeof(buf));
+               ret = read_wim_resource(lte, buf, to_read, offset, 0);
+               if (ret != 0)
+                       return ret;
+               if (check_hash)
+                       sha1_update(&ctx, buf, to_read);
+               ret = extract_chunk(buf, to_read, offset, extract_chunk_arg);
+               if (ret != 0) {
+                       ERROR_WITH_ERRNO("Error extracting WIM resource");
+                       return ret;
+               }
+               bytes_remaining -= to_read;
+               offset += to_read;
+       }
+       if (check_hash) {
+               sha1_final(hash, &ctx);
+               if (!hashes_equal(hash, lte->hash)) {
+               #ifdef ENABLE_ERROR_MESSAGES
+                       ERROR("Invalid checksum on the following WIM resource:");
+                       print_lookup_table_entry(lte, stderr);
+               #endif
+                       return WIMLIB_ERR_INVALID_RESOURCE_HASH;
+               }
+       }
+       return 0;
+}
 
-       dentry = MALLOC(sizeof(struct dentry));
-       if (!dentry) {
-               ERROR("Failed to allocate %zu bytes for root dentry!\n",
-                               sizeof(struct dentry));
-               ret = WIMLIB_ERR_NOMEM;
-               goto err1;
+/* Write @n bytes from @buf to the file descriptor @fd, retrying on internupt
+ * and on short writes.
+ *
+ * Returns short count and set errno on failure. */
+static ssize_t full_write(int fd, const void *buf, size_t n)
+{
+       const char *p = buf;
+       ssize_t ret;
+       ssize_t total = 0;
+
+       while (total != n) {
+               ret = write(fd, p, n);
+               if (ret < 0) {
+                       if (errno == EINTR)
+                               continue;
+                       else
+                               break;
+               }
+               total += ret;
+               p += ret;
        }
+       return total;
+}
 
-       /* Read the root directory entry starts after security data, on an
-        * 8-byte aligned address. 
-        *
-        * The security data starts with a 4-byte integer giving its total
-        * length. */
-       get_u32(buf, &dentry_offset);
-       dentry_offset += (8 - dentry_offset % 8) % 8;
-               
-       ret = read_dentry(buf, res_entry->original_size, dentry_offset, dentry);
-       if (ret != 0)
-               goto err1;
+int extract_wim_chunk_to_fd(const u8 *buf, size_t len, u64 offset, void *arg)
+{
+       int fd = *(int*)arg;
+       ssize_t ret = full_write(fd, buf, len);
+       if (ret < len) {
+               ERROR_WITH_ERRNO("Error writing to file descriptor");
+               return WIMLIB_ERR_WRITE;
+       } else {
+               return 0;
+       }
+}
 
-       /* This is the root dentry, so set its pointers correctly. */
-       dentry->parent = dentry;
-       dentry->next   = dentry;
-       dentry->prev   = dentry;
+/*
+ * Copies the file resource specified by the lookup table entry @lte from the
+ * input WIM to the output WIM that has its FILE * given by
+ * ((WIMStruct*)wim)->out_fp.
+ *
+ * The output_resource_entry, out_refcnt, and part_number fields of @lte are
+ * updated.
+ *
+ * (This function is confusing and should be refactored somehow.)
+ */
+int copy_resource(struct wim_lookup_table_entry *lte, void *wim)
+{
+       WIMStruct *w = wim;
+       int ret;
 
-       /* Now read the entire directory entry tree. */
-       ret = read_dentry_tree(buf, res_entry->original_size, dentry);
-       if (ret != 0)
-               goto err2;
+       if ((lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA) &&
+           !w->write_metadata)
+               return 0;
 
-       /* Calculate the full paths in the dentry tree. */
-       ret = for_dentry_in_tree(dentry, calculate_dentry_full_path, NULL);
+       ret = write_wim_resource(lte, w->out_fp,
+                                wim_resource_compression_type(lte),
+                                &lte->output_resource_entry, 0);
        if (ret != 0)
-               goto err2;
-
-       *root_dentry_p = dentry;
-       FREE(buf);
-       return ret;
-err2:
-       free_dentry_tree(dentry, NULL, false);
-err1:
-       FREE(buf);
-       return ret;
+               return ret;
+       lte->out_refcnt = lte->refcnt;
+       lte->part_number = w->hdr.part_number;
+       return 0;
 }
-
-